function createHttpRequest()
{
  var xmlHttp;
  try{
    // Firefox, Opera 8.0+, Safari
    xmlHttp=new XMLHttpRequest();
  }catch (e){
    // Internet Explorer
    try{
      xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
    }catch (e) {
      try{
        xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
      }catch (e){
        alert("Your browser does not support AJAX!");
        return false;
      }
    }
  }
  return xmlHttp;
}
